Contact structure for a power circuit breaker



Sept. I7, 1968 F. Boum 3,402,274

CONTACT STRUCTURE FOR A POWER CRCUIT BREAKER F. BOULD sept. 17, 1968 CONTACT STRUCTURE FOR A POWER CIRCUIT BREAKER 4 Sheets-Sheet 2 Filed Oct. l, 1965 /NVEN raf?. F RE D BOU/ D Sept. 17, 1968 F. BOULD 3,402,274

CONTACT STRUCTURE FOR A POWER CIRCUIT BREAKER- Filed Oct. l, 1965 4 Sheets-Sheet 5 /Nvs/vron FRE D BOULD @y im,

Sept. 17, 1968 F. BOULD 3,402,274

CONTACT STRUCTURE FOR A POWER CIRCUIT BREAKER Filed Oct. l, 1965 4 Sheets-Sheet 4 /A/vE/vro/ia FRED SOUL D @Lai/M04. W

UnitedStates Patent O 3,402,274 CONTACT STRUCTURE FOR A POWER CIRCUIT BREAKER Fred Bould, Pittsburgh, Pa., assignor to Square D Company, Park Ridge, Ill., a corporation of Michigan Filed Oct. 1, 1965, Ser. No. 491,949 7 Claims. (Cl. 20D- 146) This invention relates to a contact structure for a lowvoltage power circuit breaker and more particularly to such a contact structure in which current flows through a mounting means for a plurality of pivoted movable contact arms, which includes a single-turn winding for energizing a magnetic trip means for the circuit breaker, which ensures proper synchronism between main and arcing contacts, and which provides blow-on forces tending to keep the contacts closed for positive control of fault currents.

An object of the invention is to provide an improved circuit breaker contact structure.

A further object of the invention is to provide an improved contact structure for a circuit breaker which is of small size relative to its current rating although including a turn of a magnetic trip means.

The foregoing objects are accomplished by providing a single-piece molded insulating base which supports a pair of incoming bus bars, one of which forms a single-turn for a magnetic trip means. The other bus bar supports stationary main and arcing contacts. The single-turn portion of the first bus bar is electrically connected to a current-carrying mounting means for a plurality of movable main contact arms and a movable arcing Contact arm. All of the Contact arms are directly driven by linear movement of an operating member, uniform contact pressure being provided by a plurality of identical spring-biased, pivoted contact pressure fingers.

Further objects and advantages will become apparent from the following description wherein reference is made to the drawings, in which:

FIGURE l is a side elevation of a contact structure in accordance with this invention, the insulating base being shown in section;

FIGURE 2 is a front elevation of the contact structure of FIGURE l;

FIGURE 3 is a perspective view of the contact structure of FIGURE 1 taken generally from the top thereof and with the contact structure in open-contact position;

FIGURE 4 is a sectional view taken as indicated by the line 4-4 of FIGURE 2;

FIGURES 5 and 6 are enlarged fragmentary views showing the contact structure of FIGURE 1 in the opencontact and closed-contact positions, respectively; and

FIGURES 7, 8, and 9 are detail views showing the contact arms of the contact structure of FIGURE 1 in the open, nearly-closed, and closed positions, respectively.

Referring to the drawings, particularly FIGURES l and 2, a circuit breaker contact structure in accordance with this invention includes a strong and rigid insulating base 10, preferably molded of glass polyester, having an upper vertical wall portion 11, an intermediate vertical wall portion 12, the major portion of which is offset forwardly of the upper wall portion 11, and a lower vertical wall portion 13. Upper and lower horizontal flanges 14 and 15 and a pair of vertical side flanges 16 (only one of which is shown) extend from the rear of the base 10 at locations inwardly of the respective edges thereof, the side flanges 16 being interconnected by a medial horizontal web 17 braced by a centrally disposed integral gusset 18 extending downwardly to the rear face of a sloping portion 19 of the intermediate wall portion 12. Extending from the front of the base 1'0 are a pair of opposite vertical side flanges 22 each of which is stepped inwardly at 3,402,274 Patented Sept. 17, 1968 ICC vertically-spaced upper portions thereof as at 23 and 24 (FIGURE 2). A horizontal web 25 horizontally aligned with the web 17 interconnects the front side flanges 22. The base 10 is provided with suitable upper and lower mounting holes 26.

A line bus bar 30 preferably comprising a pair of silverplated copper plates 31 and 32 juxtaposed in face-to-face relation passes freely through a rectangular opening 34 in the upper wall portion 11 of the base 10 and is rigidly held in position by a plurality of angle brackets 35 fastened to the wall portion 11 by respective screws 36 and bolted to the bus bar 30 by respective bolts 38. A plurality of laterally-spaced holes 39 at the rearward end portion of the bus bar 30 facilitate connection thereto of a line bus (not shown).

A stationary arcing contact assembly 40 comprises a stationary arcing contact 41 preferably of silver-tungsten composition, best shown in FIGURE 4, brazed to the forward face of a lower widened portion 42 of a copper arc runner plate 44 having an upper tongue portion 45. Brazed to the rearward face of the widened portion 42 is an elongated contact block 46. The contact block 46 is secured to the upper face of the forward end portion of the bus bar 30 by a pair of cap screws 48. A sheet of insulating material 49, pierced to receive the contact block 46, is disposed between the rearward face of the widened portion 42 of the arc runner plate 44 and the forward end face of the bus bar 30 and extends beyond the side edges of the widened portion 42 thereby to prevent arcs from striking the bus bar 30 and a pair of cap screws 50 of a stationary main contact assembly.

The stationary main contact assembly comprises a main contact means in the form of a pair of elongated stationary main contacts 51 of hard-drawn copper. The contacts 51 are brazed in longitudinally-spaced relation to a contact block 52 secured to the lower face of the forward end portion of the bus bar 30 by a pair of cap screws 50.

A single-turn series trip coil 55, preferably cast from copper, comprises an upper portion 56 having -a rearward face 58 held in good electrical engagement against a front face of a lower portion 59 of a load terminal or contact support bracket 60 by a plurality of cap screws 61. The upper portion 56 overlies a lower U-shaped portion 62 having legs 63 and 64 (FIGURE 2), one side marginal area of the upper portion 56 forming a continuation of the leg 63. The leg 64 is integral with a horizontal load bus bar portion 65 which extends through a rectangular opening 66 between the wall portions 12 and 13 which opening also provides space for the heads of the screws 61. The bus bar portion 65 is secured to the base 10 by a pair of angle brackets 67 fastened to the portion 65 by respective bolts 68 and to the base portion 13 by respective screws 69. A plurality of holes 70 near the rearward end of the bus bar portion 65 facilitates connection thereto of a load bus (not shown).

The trip coil 55 thus may forrn a single-tum winding for a conventional magnetic trip means indicated by the C-shaped core structure 71 and not forming a part of this invention.

The contact support bracket 60 has an upright mounting portion 72 held to the front face of the rwall portion 12 of the base 10 by a plurality of screws 74 and a forwardly extending curved shaft-support portion 75 within `which a cylind-rical shaft 76 is secured as by a plurality of cap screws 78. The lower portion 59 of the bracket 60 is offset from the mounting portion 72 by an offsetting portion 79 complementary to the sloping portion 19 of the base 10.

A hinge frame 80 has perforated opposite depending leg portions 81 and 82 rotatably received on opposite end portions of the shaft 76, a central web portion 84, and opposite upstanding leg portions 85 and 86 which are coplanar with the depending leg portions 81 and 82 and which support a main contact pivot pin 87 held at opposite ends by respective spring clips 88. A central tongue 89 extends upwardly from the upper edge of the web portion 84.

Each of a plurality of identical contact pressure fingers 90 and 90a has a lower 4C-shaped portion 91 rotatably received on the shaft 76, an intermediate lug portion 92, and an upper bearing portion 93. To ensure good electrical contact between the fingers 90 and 90a and the shaft 76, an arcuate inner surface 94 defined by the C-shaped portion 91 has a shorter radius than the shaft 76, the arcuate surface 94 being tangent at its opposite ends to diverging straight side portions 95 (FIG- URE 4) which engage the shaft 76. The fingers 90 and 90a are arranged in several pairs along the shaft 76. In the embodiment illustrated, there are four pairs 96 (FIG- URE 3) of fingers 90 arranged with two of the pairs 96 von opposite sides of a central pair 98 of the fingers 90a.

The lug portions 92 of the two fingers 90 of each pair 96 and of the two fingers 90a of the pair 98 are secured to a loading link 100 as by a pin 101, the several links 100 passing freely through respective openings in the web portion 84 and being surrounded by respective helical springs '2 each captivated between a pair of inner and outer spring seats 104 and 105. The inner spring seats 104 bear against the web portion 84 and each of the outer spring seats 105 is retained by a pin 106 passing through an opening in the end portion of its associated link 100. The springs 102 are thus maintained compressed thereby to urge the associated pair 96 or 98 of the fingers 90 clockwise as viewed in FIGURES l and 4. A spacer 104er (FIGURE 4) may be interposed between the web portion 84 and the seat 104 of the spring 102 associated with the fingers 90a. Each pair 96 of the fingers 90 is separated from its adjacent pair 96 'by a pair of insulating washers 108, a single washer 108 being placed between the pair 98 of the fingers 90a and the adjacent pairs 96 of the fingers 90.

Each of a plurality of movable main contact arms 109 has a movable main contact 110 brazed thereon. The contact arms 109 are arranged in pairs respective to the pairs 96 of the fingers 90 and are pivoted intermediate their ends on the pin 87. Lower end portions 111 of the contact arms 109 engage the upper bearing portions 93 of the respective fingers 90 and are biased thereby about the pin 87 in a counterclockwise direction -as viewed in FIGURES 1 and 4. In the embodiment i1- lustrated, there are two pairs of the contact arms 109 adjacent one end of the pin 87 and two pairs adjacent the other end. Thus, the contact arms 109 constitute two groups near respective ends of the pin 87, the contacts 110 on one group of contact arms 109 cooperating with one of the stationary main contacts 51 and the contacts 110 on the other group of contact arms 109 cooperating with the other stationary main contact 51.

Rotatably received on the pin 87 intermediate the pairs of the movable main contact arms 109 near the opposite ends of the pin 87, respectively, are outer leg portions 114 and 115 of a hinge fork 116, the fork 116 also having two intermediate spaced leg portions 118 and 119 rotatably received on the pin 87 between the two groups of the contact arms 109. The leg portions 118 and 119 have upper tongue portions carrying an arcing contact pivot pin 120 secured by a cotter 120a and which rotatably supports, between the leg portions 118 and 119, a movable arcing contact arm 121 having a movable arcing contact 122 brazed thereon and including an arc runner portion 124 and an inwardly curved depending portion 125 engaging the bearing portions 93 of the central pair 98 of the ngers 90a. As will be explained, the movable arcing contact 122 engages the stationary arcing contact 41.

From the foregoing, it will be seen that when the contact structure is in the open position, the lsprings 102 urge the contact pressure fingers and 90a clockwise about the shaft 76 as viewed in FIGURE 4 thereby to urge the contact arms 109 counterclockwise about the pin 87 and the contact arm 121 counterclockwise about the pin 120, the web portion 84 serving a stop for both the arms 109 and 121. The spacer 104a shortens the effective length of the spring 102 associated with the fingers 90a to provide an increased bias for the arcing contact arm 121.

The hinge fork 116 has a socket threaded to receive one end of a coupling 128, the other end portion of which is threaded into a socket in a drive link 129 of a circuit breaker operating mechanism not otherwise shown. The fork 116, the coupling 128, and the drive link 129 may be considered as constituting an operating member for the contact structure.

It should be noted that the configuration of the contact structure is such that upon liow of high fault currents through the contact structure, the magnetic forces are such as to hold the contacts in their closed position.

In operation, movement of the drive link 129 linearly in a direction to close the contacts of the contact structure exerts force on the pin 87 through the coupling 128 and the fork 116 thereby to drive the contact frame 80 counterclockwise about the shaft 76 and the contact arms 109 and 121 toward the stationary contacts 41 and 51 from the open-contact position of FIGURE 7 through the position of FIGURE `8 to the closed-contact position of FIGURE 9. Because of the difference in shape of the arcing contact arm 121 and the spacing between the shafts 87 and 120, the arcing contacts 41 and 122 engage before the main contacts 51 land 110. It is to 'be noted, by a comparison of FIGURES 7 and 8, that the fingers 90a of the pai-r 98 move clockwise relative to the fingers 90 of the pairs 96 during initial movement of the link 129 thereby to cause the arcing contact arm 121 to rotate counterclockwise with respect to the main contact `arms 109.

Upon engagement of the arcing contacts 41 and 122, the arcing contact arm 121 rotates clockwise about its pivot pin against the force exerted thereon by the pair of contact pressure fingers 90a. Further movement of the drive link 129 in the closing direction causes engagement of the main contacts 51 and 110. Upon such engagement, the main contact arms 109 rotate clockwise about their pivot shaft 87 against the force exerted thereon by the respective contact pressure fingers 90. The pressure between the contacts 41 and 122 and between the contacts 51 and the cont-acts 110 is determined by the springs 102 which are further compressed as the contacts engage.

Movement of the drive link 128 in the opening direction from a closed position of the contact structure causes the main contacts 51 and 110 to separate first followed by separation of the Iarcing contacts 41 and 122 as is apparent from a comparison of FIGURES 8 and 9.

I claim:

1. A contact structure for a low-voltage power circuit breaker, said contact structure comprising a stationary arcing contact, a stationary main contact means, a main shaft, a frame pivoted on said shaft and carrying a main contact pivot pin, a plurality of main contact arms pivoted on said main contact pivot pin in axially spaced relation therealong, an operating member pivoted on said main contact pivot pin and carrying an arcing contact pivot pin, a movable arcing contact arm pivoted on said arcing contact pivot pin, a plurality of contact pressure fingers pivoted on said main shaft in axially spaced `relation therealong, a plurality of springs operatively interposed between said fingers and said frame and biasing said fingers with respect to said frame, said arcing contact arm having a depending portion engaging at least one of said fingers, said main contact arms having depending portions engaging others of said fingers, respectively, said springs urging said iingers about said main shaft in one direction thereby to urge said contact arms in the opposite direction about their associated pivot pins, and said operating member being movable to rotate said frame about said main shaft thereby to move said main contact arms into engagement with said stationary main contact means and said arcing contact arm into engagement with said stationary arcing contact, said engagement of said contact arms urging said depending portions against their associated fingers thereby to further compress said springs.

2. A contact structure in accordance with claim 1 characterized in that an insulating base is provided, said stationary arcing contact is carried by the lbase near the top thereof, and said stationary main contact means is carried by the base immediately below the stationary arcing contact.

3. A contact structure in accordance with claim 2 characterized in that a line bus bar extends .rearwardly of the base member and is electrically connected to said stationary main contact means and to said stationary arcing contact.

4. A contact structure in accordance with claim 3 characterized in that an integral load bus bar and magnetic trip winding are mounted on said base member below said stationary main Contact means, and connecting means are provided to electrically connect said magnetic trip winding to said main shaft.

5. A contact structure in accordance with claim '4 characterized in that said connecting means is a support bracket for said main shaft.

6. A contact structure for a low-voltage power circuit breaker, said contact structure comprising an insulating base, a Stationary arcing contact carried by the base near the top thereof, a stationary main contact means carried by the base immediately below the stationary arcing contact, a line bus bar extending rearwardly of the base and electrically connected to said stationary arcing contact and to said stationary main contact means, an integral load bus bar and magnetic trip winding mounted on said base below said stationary main contact means, a contact support bracket mounted on said base and electrically connected to said winding, a main shaft iixed to said support bracket, a frame pivoted on said shaft and carrying a Imain contact pivot pin, a plurality of main contact arms pivoted on said main contact pivot pin in axially spaced relation therealong, an operating member pivoted on said main contact pivot pin and carrying an arcing contact pivot pin, a movable arcing contact arm pivoted on said arcing contact pivot pin, a plurality of contact pressure fingers pivoted on said main shaft in axially spaced relation therealong, a plurality of springs operatively interposed between respective pairs of said fingers and said frame and biasing said fingers with respect to said frame, said arcing contact arm having a depending portion engaging a pair of said fingers, said main contact arms having depending portions engaging the others of said fingers, respectively, said springs urging said fingers about said main shaft in one direction thereby to urge said contact arms in the opposite direction about their associated pivot pins, and said operating member being movable to rotate said frame about said main shaft thereby to move said main contact arms into engagement with said stationary main contact means and said arcing contact arm into engagement with said stationary arcing contact, said engagement of said contact arms urging said depending portions against their associated fingers thereby to further compress said springs.

7. A contact structure in accordance with claim 6 characterized in that said arcing contact pin is disposed above said main contact pin.

References Cited UNITED STATES PATENTS 2,302,394 11/1942 Seaman ZOO-146 3,218,428 11/1965 Gauthier 200-146 X 3,345,486 10/1967 Engel 200-146 ROBERT S. MACON, Primary Examiner.

U.S. DEPARTMENT 0F COMMERCE PATENT OFFICE Washington, D.C. 20231 UNITED STATES PATENT OEEICE CERTIFICATE 0F CORRECTION Patent No. 3 ,402 ,274 September 17 1968 Pred Bould It is certified that error' appears in the a'bove identified patent and that said Letters Patent are hereby corrected as show-n below:

Column 6, line 37, "3,345,486" should read 3,345,485

Signed and sealed this 10th day of February 1970.

(SEAL) Attest:

Edward M. Fletcher, J r.

Commissioner of Patents Attesting Officer WILLIAM E. SCHUYLER, JR. 

1. A CONTACT STRUCTURE FOR A LOW-VOLTAGE CIRCUIT BREAKER, SAID CONTACT STRUCTURE COMPRISING A STATIONARY ARCING CONTACT, A STATIONARY MAIN CONTACT MEANS, A MAIN SHAFT, A FRAME PIVOTED ON SAID SHAFT AND CARRYING A MAIN CONTACT PIVOT PIN, A PLURALITY OF MAIN CONTACT ARMS PIVOTED ON SAID MAIN CONTACT PIVOT PIN IN AXIALLY SPACED RELATION THEREALONG, AN OPERATING MEMBER PIVOTED ON SAID MAIN CONTACT PIVOT PIN AND CARRYING AN ARCING CONTACT PIVOT PIN, A MOVABLE ARCING CONTACT ARM PIVOTED ON SAID ARCING CONTACT PIVOT PIN, A PLURALITY OF CONTACT PRESSURE FINGERS PIVOTED ON SAID MAIN SHAFT IN AXIALLY SPACED RELATION THEREALONG, A PLURALITY OF SPRINGS OPERATIVELY INTERPOSED BETWEEN SAID FINGERS AND SAID FRAME AND BIASING SAID FINGERS WITH RESPECT TO SAID FRAME, SAID ARCHING CONTACT ARM HAVING 